Japanese Laid-open Patent Publication No. 2005-286892 discloses an oscillator that is formed as single chip by combining a vibrator made of silicon (Si), a temperature sensor for detecting the temperature of the vibrator, and peripheral circuits such as a phase-locked loop (PLL), thereby minimizing the frequency variation of the vibrator according to the detected temperature.
On such a chip, circuits can be formed using a CMOS process, since the vibrator is also made of Si.